The Presence of CA19‐9 in Serum and Saliva from Lewis Blood‐group Negative Cancer Patients

Eighteen cancer patients showed high levels of CA19‐9 in sera, even though the blood‐group phenotypes of their red blood cells were Le(a — b —). Seven of these patients (group I) were determined as Le(a — b —) from both red blood cells and saliva consistently, whereas eleven other patients (group II) secreted either Le^a or Le^b antigen in saliva and showed the expression of incompatible Lewis blood‐group antigens. GDP‐fucose: N‐acetyl‐glucosaminide a(1 × 4)‐L‐fucosyltransferase was demonstrated to be present in salivas from both group I and group II. These results suggest that a cancer‐associated alteration of Lewis blood‐group antigen expression occurs in cancer patients.